Polyester-polycarbonate blends useful for extrusion blow-molding

ABSTRACT

Blends of polycarbonate and copolyester that are capable of being extrusion blow-molded are described. The blends preferably comprise (I) about 1 to 99% by weight of a linear or branched polycarbonate and (II) about 1 to 99% by weight of a mixture of (i) about 40 to 100% by weight of a first copolyester and (ii) about 0 to 60% by weight of a second copolyester. The first copolyester preferably comprises (A) diacid residues comprising terephthalic acid residues, (B) diol residues comprising about 45 to 75 mole percent of 1,4-cyclohexanedimethanol (CHDM) residues and about 25 to 55 mole percent of ethylene glycol residues, and (C) about 0.05 to 1.0 mole percent of the residue of a trifunctional monomer. The optional second copolyester preferably comprises (A) diacid residues comprising terephthalic acid residues and (B) diol residues comprising about 52 to 90 mole percent of CHDM residues and about 10 to 48 mole percent of ethylene glycol residues. Preferably, the average amount of CHDM residues in the copolyester mixture II ranges from 52 to 75 mole percent. It has been surprisingly found that the presence of the trifunctional residues in the first copolyester can impart sufficient melt strength for the blends to be extrusion blow-molded. Containers and shaped articles made from the blends as well as a method of making the articles are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of the filing date of U.S.Provisional Patent Application No. 60/439,681, filed on Jan. 13, 2003,under 35 U.S.C. 3 119(e). The entire content of the '681 application ishereby incorporated by reference.

FIELD OF THE INVENTION

[0002] This invention generally relates to blends of polycarbonate andcopolyesters that are capable of being extrusion blow-molded. Theinvention also relates to containers and shaped articles made from theblends as well as a method of making the articles.

BACKGROUND OF THE INVENTION

[0003] Various types of containers currently made from glass are beingreplaced by plastic containers due to the weight, bulkiness, andsusceptibility to breakage inherent in glass containers. In many cases,these containers can be manufactured from existing polymers, such as thepolyesters described in U.S. Pat. No. 4,983,711. Polyvinylchloride (PVC)and polycarbonate (PC) are other materials often used for extrusionblow-molded containers. In certain circumstances, however, thesepolymers do not meet fitness-for-use criteria when used in their neatform. For example, when the containers must contain liquids hotter than75° C., the polyesters described in the '711 patent and PVC are notadequate due to low softening points. Similarly, polycarbonate is oftenunacceptable in the same applications due to poor chemical resistance tothe contents or cleaners used during processing of the bottles. Inaddition, polycarbonate often requires complicated annealing proceduresto remove residual stresses formed during processing.

[0004] In order to take advantage of selected properties of differentpolymers, for example, high temperature resistance and good chemicalresistance, they are often blended together. However, not all blends aretransparent; thus, the selection of materials that can be blendedtogether is further limited by the need to create transparentcontainers.

[0005] Blends of polycarbonate and certain polyesters are used ininjection molding and sheet extrusion applications. These blends areclear and can provide a good balance of chemical resistance and heatresistance. However, existing commercial transparent blends ofpolycarbonate and polyesters cannot be processed by extrusionblow-molding due to lack of melt strength.

[0006] Manufacturing equipment and processes have been designed and putinto use for the cost-efficient production of various types and sizes ofcontainers at high rates. One of these manufacturing processes isextrusion blow-molding wherein a polymer melt is extruded from a diedownward in the shape of a hollow cylinder or tube. Bottles and othershaped articles are produced by clamping a mold around the molten,hollow cylinder and injecting a gas, e.g., air, into the molded-encasedcylinder to force the molten polymer into the mold. For a polymer to beuseful in extrusion blow-molding processes, the polymer should possesssufficient melt strength. To be useful for the production of rigid(self-supporting) containers, especially relatively large containers,e.g., containers intended for packaging volumes of 3 L or greater, andcontainers having an irregular shape, the polymer should also possessadequate physical, tensile, and thermal properties.

[0007] Many polymeric materials do not possess melt strength sufficientto render them suitable for extrusion blow-molding, and when extrudeddownward from a die, the polymer melt drops rapidly and forms a thinstring and/or breaks. Polymers suitable for extrusion blow-molding havea melt strength that is sufficient to support the weight of the polymer.Good melt strength is desired for the manufacture by extrusionblow-molding of containers having uniform wall thickness.

[0008] Since melt strength is related to slow flow, which is inducedprimarily by gravity, melt strength can be related to the viscosity of apolymer measured at a low shear rate, such as 1 radian/second. Viscositycan be measured by typical viscometers, such as a parallel plateviscometer. Typically, viscosity is measured at the typical processingtemperature for the polymer and is measured at a series of shear rates,often between 1 radian/second and 400 radian/second. In extrusionblow-molding, the viscosity at 1 radian/second at processingtemperatures typically needs to be above 30,000 poise in order to blow abottle. Larger parisons require higher viscosities.

[0009] Melt strength, however, only defines one of the polymerprocessing characteristics desired in extrusion blow-molding. Anotherdesired characteristic is the ease of flow at high shear rates. Thepolymer is “melt processed” at shear rates ranging anywhere from about10 s⁻¹ to 1000 s⁻¹ in the die/extruder. A typical shear rate encounteredin the barrel or die during extrusion blow-molding or profile extrusionis 400 radians/second. These high shear rates are encountered as thepolymer flows down the extruder screw, or as it passes through the die.These high shear rates are desired to maintain reasonably fastproduction rates. Unfortunately, high melt viscosity at high shear ratescan lead to viscous dissipation of heat, in a process referred to asshear heating. Shear heating raises the temperature of the polymer, andthe extent of temperature rise is directly proportional to the viscosityat that shear rate. Since viscosity decreases with increasingtemperature, shear heating decreases the low shear rate viscosity of thepolymer, and thus, its melt strength decreases.

[0010] Furthermore, a high viscosity at high shear rates (for example,as found in the die) can create a condition known as melt fracture or“sharkskin” on the surface of the extruded part or article. Meltfracture is a flow instability phenomenon occurring during extrusion ofthermoplastic polymers at the fabrication surface/polymer melt boundary.The occurrence of melt fracture produces severe surface irregularitiesin the extrudate as it emerges from the orifice. The naked eye detectsthis surface roughness in the melt-fractured sample as a frostyappearance or matte finish as opposed to an extrudate without meltfracture that appears clear. Melt fracture can occur whenever the wallshear stress in the die exceeds a certain value, typically 0.1 to 0.2MPa. The wall shear stress is directly related to the volume throughputor line speed (which dictates the shear rate) and the viscosity of thepolymer melt. By reducing either the line speed or the viscosity at highshear rates, the wall shear stress is reduced, lowering the possibilityfor melt fracture to occur. Although the exact shear rate at the diewall is a function of the extruder output and the geometry and finish ofthe tooling, a typical shear rate that is associated with the onset ofmelt fracture is 400 radian/sec. Likewise, the viscosity at this shearrate typically needs to be below 10,000 poise.

[0011] To couple all of these desired properties, the ideal extrusionblow-molding polymer, from a processability standpoint, will possess ahigh viscosity at low shear rates in conjunction with a low viscosity athigh shear rates. Fortunately, most polymers naturally exhibit at leastsome degree of viscosity reduction between low and high shear rates,known as “shear thinning”, which aids in their processability. Based onthe preceding discussion, one definition of shear thinning relevant toextrusion blow-molding would be the ratio of the viscosity measured at 1radian/second to the viscosity measured at 400 radians/second when bothviscosities are measured at the same temperature. The measurementtemperature selected should be typical of the actual processingconditions and one that provides a viscosity of 10,000 poise or less at400 rad/sec. This definition will be used to describe shear thinning forthe purposes of this invention. Based on the preceding discussion, agood extrusion blow-molding material would possess a shear thinningratio of 3.0 or higher when measured at a temperature that provides aviscosity at 400 rad/sec of 10,000 poise or less.

SUMMARY OF THE INVENTION

[0012] In one aspect, the invention relates to a blend that is capableof being extrusion blow-molded. The blend comprises:

[0013] I. about 1 to 99 weight percent of a polycarbonate comprising adiol component comprising about 90 to 100 mole percent of4,4′-isopropylidenediphenol units and about 0 to 10 mol percentmodifying diol units having 2 to 16 carbon atoms; and

[0014] II. about 1 to 99 weight percent of a mixture comprising:

[0015] A. about 40 to 100 weight percent of a first copolyester thatpreferably has an inherent viscosity of about 0.5 to 1.1 and a shearthinning ratio of at least about 5, and comprises:

[0016] (1) diacid residues comprising terephthalic acid residues;

[0017] (2) diol residues comprising about 45 to 75 mole percent of1,4-cyclohexanedimethanol residues and about 25 to 55 mole percent ofethylene glycol residues; and

[0018] (3) about 0.05 to 1.0 mole percent of the residue of atrifunctional monomer; and

[0019] B. about 0 to 60 weight percent of a second copolyestercomprising:

[0020] (1) diacid residues comprising terephthalic acid residues; and

[0021] (2) diol residues comprising about 52 to 90 mole percent1,4-cyclohexanedimethanol residues and about 10 to 48 mole percentethylene glycol residues,

[0022] wherein the average amount of 1,4-cyclohexanedimethanol residuesin the first and second copolyesters is between 52 to 75 mole percent.

[0023] In a preferred embodiment, the blend comprises between 45 and 90weight percent of the copolyester mixture and between 10 and 55 weightpercent of the polycarbonate, and the first copolyester preferably hasan inherent viscosity of about 0.5 to 1.1 and a shear thinning ratio ofat least about 5, and comprises:

[0024] A. diacid residues comprising terephthalic acid residues;

[0025] B. diol residues comprising about 52 to 75 mole percent of1,4-cyclohexanedimethanol residues and about 25 to 48 mole percent ofethylene glycol residues; and

[0026] C. about 0.05 to 1.0 mole percent of the residue of atrifunctional monomer.

[0027] In another aspect, the invention relates to a method of making aclear article. The method comprises the steps of:

[0028] (a) blending a polycarbonate, a first copolyester, and optionallya second copolyester;

[0029] (b) before, during, or after step (a), melting the polycarbonate,the first copolyester, and optionally the second copolyester to form amelt blend; and

[0030] (c) cooling the melt blend to form a clear article.

[0031] In another aspect, the invention relates to shaped articlesextrusion blow-molded from the blends according this invention.

[0032] In yet another aspect, the invention relates to containersextrusion blow-molded from the blends according this invention.

DETAILED DESCRIPTION OF THE INVENTION

[0033] It has been surprisingly found that certain copolyesters can beblended with polycarbonate to provided sufficient melt strength forextrusion blow-molding. The resultant blends are clear and do notproduce problems with crystallization during the extrusion blow-moldingprocess. Preferably, the blends have a shear thinning ratio of at leastabout 3 and are comprised of (A) about 1 to 99% (more preferably, 10 to55%) by weight of a linear or branched polycarbonate and (B) about 1 to99% (more preferably, 45 to 90%) by weight of a mixture of 40 to 100% byweight of a first copolyester and 0 to 60% by weight of a secondcopolyester. Preferably, the average amount of 1,4-cyclohexanedimethanolresidues in the mixture of the first copolyester and the secondcopolyester ranges from 52 to 75 mole percent.

[0034] The first copolyesters provided by our invention preferably havean inherent viscosity of about 0.5 to 1.1 and a shear thinning ratio ofat least about 5, and are comprised of:

[0035] A. diacid residues comprising terephthalic acid residues;

[0036] B. diol residues comprising about 45 to 75 mole percent1,4-cyclohexanedimethanol residues and about 25 to 55 mole percentethylene glycol residues; and

[0037] C. about 0.05 to 1.0 mole percent of the residue of atrifunctional monomer.

[0038] An especially preferred group of the first copolyesters has aninherent viscosity of about 0.6 to 0.9 and a shear thinning ratio of atleast about 5, and comprises:

[0039] A. diacid residues consisting essentially of terephthalic acidresidues;

[0040] B. diol residues consisting essentially of about 52 to 75 molepercent of 1,4-cyclohexanedimethanol residues and about 25 to 48 molepercent of ethylene glycol residues; and

[0041] C. about 0.1 to 0.25 mole percent of trimellitic acid oranhydride residues.

[0042] An optional second copolyester provided by our inventionpreferably has an inherent viscosity of about 0.5 to 1.1 and a shearthinning ratio of at least about 2, and is comprised of:

[0043] A. diacid residues comprising terephthalic acid residues;

[0044] B. diol residues comprising about 52 to 90 mole percent1,4-cyclohexanedimethanol residues and about 10 to 48 mole percentethylene glycol residues.

[0045] These copolyesters have been found to be useful for making blendswith polycarbonate that can be extrusion blow-molded to producetransparent, noncrystalline articles such as containers. Thesecontainers exhibit good resistance to deformation when filled withliquids heated up to 85° C., and some compositions exhibit goodresistance to deformation when filled with liquids heated up to 100° C.(boiling point of water). It has been surprisingly found that thepresence of the trifunctional residues in the first copolyester canimpart sufficient melt strength for the blends to be extrusionblow-molded even when non-branched polycarbonate is used in the blends.

[0046] Preferably, diacid residues A contain at least 40 mole percent,and more preferably 100 mole percent, of terephthalic acid residues. Theremainder of the diacid component A may be made up of one more alicyclicand/or aromatic dicarboxylic acid residues commonly present inpolyesters. Examples of such dicarboxylic acids include 1,2-, 1,3- and1,4-cyclohexanedicarboxylic; 2,6- and 2,7-naphthalenedicarboxylic;isophthalic; and the like. Diacid residues A may be derived from thedicarboxylic acids or from ester forming derivatives thereof such asdialkyl esters or acids chlorides.

[0047] The trifunctional residues C can be derived from tricarboxylicacids or ester forming derivatives thereof such as trimellitic(1,2,4-benzenetricarboxylic) acid and anhydride, hemimellitic(1,2,3-benzenetricarboxylic) acid and anhydride, trimesic(1,3,5-benzenetricarboxylic) acid, and tricarballyic(1,2,3-propanetricarboxylic) acid. Generally, any tricarboxyl residuecontaining about 6 to 9 carbon atoms may be used as component C. Thetrifunctional residue may also be derived from an aliphatic triolcontaining about 3 to 8 carbon atoms such as glycerin,trimethylolethane, and trimethylolpropane. The amount of thetrifunctional monomer residue present in the first copolyester ispreferably in the range of about 0.10 to 0.25 mole percent. Thepreferred trifunctional monomer residues are residues ofbenzenetricarboxylic acids (including anhydrides), especiallytrimellitic acid or anhydride.

[0048] The mole percentages referred to herein are based on 100 molepercent (or the total number of moles) of the particular component inquestion. For example, the expression “diacid residues comprising atleast 40 mole percent terephthalic residues” means that at least 40percent of the moles of diacid residues in the copolyester areterephthalic residues. The balance of the diacid residues can be someother species. The mole percent of the trifunctional component C in thefirst copolyester is based on (1) the moles of diacid component A whencomponent C is a triacid residue or (2) the moles of diol component Bwhen component C is a triol residue.

[0049] When the word “about” precedes a numerical range, it is intendedthat the word modifies both the lower as well as the higher value of therange.

[0050] When the blend comprises a mixture of copolyesters, an especiallypreferred group of our first copolyesters has an inherent viscosity ofabout 0.6 to 0.9 and a shear thinning ratio of at least about 5, and iscomprised of:

[0051] A. diacid residues consisting essentially of terephthalic acidresidues;

[0052] B. diol residues consisting essentially of about 48 to 65 molepercent 1,4-cyclohexanedimethanol residues and about 35 to 52 molepercent ethylene glycol residues; and

[0053] C. about 0.1 to 0.25 mole percent of trimellitic acid oranhydride residues.

[0054] The copolyesters of our invention may be prepared usingprocedures well known in the art for the preparation of high molecularweight polyesters. For example, the copolyesters may be prepared bydirect condensation using a dicarboxylic acid or by ester interchangeusing a dialkyl dicarboxylate. Thus, a dialkyl terephthalate such asdimethyl terephthalate is ester interchanged with the diols at elevatedtemperatures in the presence of a catalyst. Polycondensation is carriedout at increasing temperatures and at reduced pressures until acopolyester having the desired inherent viscosity is obtained. Theinherent viscosities (I.V., dl/g) reported herein were measured at 25°C. using 0.5 g polymer per 100 mL of a solvent consisting of 60 parts byweight phenol and 40 parts by weight tetrachloroethane. The molepercentages of the diol residues of the polyesters were determined bynuclear magnetic resonance.

[0055] Examples of the catalyst materials that may be used in thesynthesis of the polyesters utilized in the present invention includetitanium, manganese, zinc, cobalt, antimony, gallium, lithium, calcium,silicon, and germanium. Such catalyst systems are described in U.S. Pat.Nos. 3,907,754; 3,962,189; 4,010,145; 4,356,299; 5,017,680; 5,668,243;and 5,681,918, the contents of which are herein incorporated byreference in their entirety. Preferred catalyst metals include titaniumand manganese and most preferred is titanium. The amount of catalyticmetal used may range from about 5 to 100 ppm, but the use of catalystconcentrations of about 5 to 35 ppm titanium is preferred in order toprovide polyesters having good color, thermal stability, and electricalproperties. Phosphorus compounds frequently are used in combination withthe catalyst metals, and any of the phosphorus compounds normally usedin making polyesters may be used. Up to about 100 ppm phosphorustypically may be used.

[0056] The polycarbonate portion of the present blend preferably has adiol component containing about 90 to 100 mole percent bisphenol Aunits, and 0 to about 10 mole percent can be substituted with units ofother modifying aliphatic or aromatic diols, besides bisphenol A, havingfrom 2 to 16 carbons. The polycarbonate can contain branching agents,such as tetraphenolic compounds, tri-(4-hydroxyphenyl) ethane,pentaerythritol triacrylate and others discussed in U.S. Pat. Nos.6,160,082; 6,022,941; 5,262,51; 4,474,999; and 4,286,083. Other suitablebranching agents are mentioned herein below. It is preferable to have atleast 95 mole percent of diol units in the polycarbonate being bisphenolA. Suitable examples of modifying aromatic diols include the aromaticdiols disclosed in U.S. Pat. Nos. 3,030,335 and 3,317,466.

[0057] The inherent viscosity of the polycarbonate portion of the blendsaccording to the present invention is preferably at least about 0.3dL/g, more preferably at least 0.5 dL/g, determined at 25° C. in 60/40wt/wt phenol/tetrachloroethane.

[0058] The melt flow of the polycarbonate portion of the blendsaccording to the present invention is preferably between 1 and 20, andmore preferably between 2 and 18, as measured according to ASTM D1238 ata temperature of 300° C. and using a weight of 1.2 kg.

[0059] The polycarbonate portion of the present blend can be prepared inthe melt, in solution, or by interfacial polymerization techniques wellknown in the art. Suitable methods include the steps of reacting acarbonate source with a diol at a temperature of about 0° C. to 315° C.at a pressure of about 0.1 to 760 mm Hg for a time sufficient to form apolycarbonate. Commercially available polycarbonates that can be used inthe present invention, are normally made by reacting an aromatic diolwith a carbonate source such as phosgene, dibutyl carbonate, or diphenylcarbonate, to incorporate 100 mol percent of carbonate units, along with100 mol percent diol units into the polycarbonate. For examples ofmethods of producing polycarbonates, see U.S. Pat. Nos. 5,498,688;5,494,992; and 5,489,665, which are incorporated by reference in theirentirety.

[0060] Processes for preparing polycarbonates are known in the art. Thelinear or branched polycarbonate that can be used in the inventiondisclosed herein is not limited to or bound by the polycarbonate type orits production method. Generally, a dihydric phenol, such as bisphenolA, is reacted with phosgene with the use of optional mono-functionalcompounds as chain terminators and tri-functional or higher functionalcompounds as branching or crosslinking agents. Reactive acyl halides arealso condensation polymerizable and have been used in polycarbonates asterminating compounds (mono-functional), comonomers (di-functional), orbranching agents (tri-functional or higher).

[0061] One method of forming branched polycarbonates, disclosed, forexample, in U.S. Pat. No.4,001,884, involves the incorporation of anaromatic polycarboxylic acid or functional derivative thereof in aconventional polycarbonate-forming reaction mixture. The examples in the'884 patent demonstrate such incorporation in a reaction in whichphosgene undergoes reaction with a bisphenol, under alkaline conditionstypically involving a pH above 10. Experience has shown that a preferredaromatic polycarboxylic acid derivative is trimellitic acid trichloride.Also disclosed in the aforementioned patent is the employment of amonohydric phenol as a molecular weight regulator; it functions as achain termination agent by reacting with chloroformate groups on theforming polycarbonate chain.

[0062] U.S. Pat. No. 4,367,186 disclose a process for producingcross-linked polycarbonates wherein a cross-linkable polycarbonatecontains methacrylic acid chloride as a chain terminator. A mixture ofbisphenol A, aqueous sodium hydroxide, and methylene chloride isprepared. To this is added a solution of methacrylic acid chloride inmethylene chloride. Then, phosgene is added, and an additional amount ofaqueous sodium hydroxide is added to keep the pH between 13 and 14.Finally, the triethylamine coupling catalyst is added.

[0063] EP 273 144 discloses a branched poly(ester)carbonate which is endcapped with a reactive structure of the formula —C(O)—CH═CH—R, wherein Ris hydrogen or C₁₋₃ alkyl. This polycarbonate is prepared in aconventional manner using a branching agent, such as trimellityltrichloride and an acryloyl chloride to provide the reactive end groups.According to the examples, the process is carried out by mixing water,methylene chloride, triethylamine, bisphenol A, and optionallypara-t-butyl phenol as a chain terminating agent. The pH is maintainedat 9 to 10 by addition of aqueous sodium hydroxide. A mixture ofterephthaloyl dichloride, isophthaloyl dichloride, methylene chloride,and optionally acryloyl chloride, and trimellityl trichloride is addeddropwise. Phosgene is then introduced slowly into the reaction mixture.

[0064] Randomly branched polycarbonates and methods of preparing themare known from U.S. Pat. No. 4,001,184. At least 20 weight percent of astoichiometric quantity of a carbonate precursor, such as an acyl halideor a haloformate, is reacted with a mixture of a dihydric phenol and atleast 0.05 mole percent of a polyfunctional aromatic compound in amedium of water and a solvent for the polycarbonate. The medium containsat least 1.2 mole percent of a polymerization catalyst. Sufficientalkali metal hydroxide is added to the reaction medium to maintain a pHrange of 3 to 6, and then sufficient alkali metal hydroxide is added toraise the pH to at least 9 but less than 12 while reacting the remainingcarbonate precursor.

[0065] U.S. Pat. No. 6,225,436 discloses a process for preparingpolycarbonates which allows the condensation reaction incorporation ofan acyl halide compound into the polycarbonate in a manner which issuitable in batch processes and in continuous processes. Such acylhalide compounds can be mono-, di-, tri- or higher-functional and arepreferably for branching or terminating the polymer molecules orproviding other functional moieties at terminal or pendant locations inthe polymer molecule.

[0066] U.S. Pat. No. 5,142,088 discloses the preparation of branchedpolycarbonates, and more particularly to novel intermediates useful inthe preparation and a method for conversion of the intermediates viachloroformate oligomers to the branched polycarbonates. One method formaking branched polycarbonates with high melt strength is a variation ofthe melt-polycondensation process where the diphenyl carbonate andBisphenol A are polymerized together with polyfunctional alcohols orphenols as branching agents.

[0067] DE 19727709 discloses a process to make branched polycarbonate inthe melt-polymerization process using aliphatic alcohols. It is knownthat alkali metal compounds and alkaline earth compounds, when used ascatalysts added to the monomer stage of the melt process, will not onlygenerate the desired polycarbonate compound, but also other productsafter a rearrangement reaction known as the “Fries” rearrangement. Thisis discussed in U.S. Pat. No. 6,323,304. The presence of the Friesrearrangement products in a certain range can increase the melt strengthof the polycarbonate resin to make it suitable for bottle and sheetapplications. This method of making a polycarbonate resin with a highmelt strength has the advantage of having lower raw material costscompared with the method of making a branched polycarbonate by adding“branching agents.” In general, these catalysts are less expensive andmuch lower amounts are required compared to the branching agents.

[0068] JP 09059371 discloses a method for producing an aromaticpolycarbonate in the presence of a polycondensation catalyst, withoutthe use of a branching agent, which results in a polycarbonatepossessing a branched structure in a specific proportion. In particular,JP 09059371 discloses the fusion-polycondensation reaction of a specifictype of aromatic dihydroxy compound and diester carbonate in thepresence of an alkali metal compound and/or alkaline earth metalcompound and/or a nitrogen-containing basic compound to produce apolycarbonate having an intrinsic viscosity of at least 0.2. Thepolycarbonate is then subject to further reaction in a specialself-cleaning style horizontal-type biaxial reactor having a specifiedrange of the ratio L/D of 2 to 30 (where L is the length of thehorizontal rotating axle and D is the rotational diameter of thestirring fan unit). JP 09059371 teaches the addition of the catalystsdirectly to the aromatic dihydroxy compound and diester carbonatemonomers.

[0069] U.S. Pat. No. 6,504,002 discloses a method for production of abranched polycarbonate composition, having increased melt strength, bylate addition of branch-inducing catalysts to the polycarbonate oligomerin a melt polycondensation process, the resulting branched polycarbonatecomposition, and various applications of the branched polycarbonatecomposition. The use of polyhydric phenols having three or more hydroxygroups per molecule, for example, 1,1,1-tris-(4-hydroxyphenyl)ethane(THPE), 1,3,5-tris-(4-hydroxyphenyl)benzene,1,4-bis-[di-(4-hydroxyphenyl)phenylmethyl]benzene, and the like, asbranching agents for high melt strength blow-moldable polycarbonate 30resins prepared interfacially has been described in U.S. Pat. Nos. Re.27,682 and 3,799,953.

[0070] Other methods known to prepare branched polycarbonates throughheterogeneous interfacial polymerization methods include the use ofcyanuric chloride as a branching agent (U.S. Pat. No. 3,541,059),branched dihydric phenols as branching agents (U.S. Pat. No. 4,469,861),and 3,3-bis-(4-hydroxyaryl)-oxindoles as branching agents (U.S. Pat. No.4,185,009). Additionally, aromatic polycarbonates end-capped withbranched alkyl acyl halides and/or acids and said to have improvedproperties are described in U.S. Pat. No.4,431,793.

[0071] Trimellitic triacid chloride has also been used as a branchingagent in the interfacial preparation of branched polycarbonate. U.S.Pat. No. 5,191,038 discloses branched polycarbonate compositions havingimproved melt strength and a method of preparing them from aromaticcyclic polycarbonate oligomers in a melt equilibration process.

[0072] The novel polymer blends of the present invention preferablycontain a phosphorus catalyst quencher component, typically one or morephosphorus compounds such as a phosphorus acid, e.g., phosphoric and/orphosphorous acids, or an ester of a phosphorus acid such as a phosphateor phosphite ester. Further examples of phosphorus catalyst quenchersare described in U.S. Pat. Nos. 5,907,026 and 6,448,334. The amount ofphosphorus catalyst quencher present typically provides an elementalphosphorus content of about 0 to 0.5 weight percent, preferably 0.1 to0.25 weight percent, based on the total weight of the blend.

[0073] The blends may also include other additives, such as heatstabilizers, UV stabilizers, antioxidants, UV absorbers, mold releases,biocides, plasticizers, or fillers such as clay, mica, talc, ceramicspheres, glass spheres, glass flakes, and the like. Additives such asthese are typically used in relatively small quantities. These additivesmay be incorporated into the blends of the invention by way ofconcentrates. These concentrates may use polyesters that are not of thecomposition described above. If so, these other polyesters arepreferably not added in quantities exceeding 5 weight percent.

[0074] The blends may be prepared using procedures well known in the artincluding, but not restricted to, compounding in a single screwextruder, compounding in a twin screw extruder, or simply pelletblending the components together prior to extrusion blow-molding.

[0075] A typical method of preparing the blends involves 1) addingpellets of the polycarbonate, the first copolyester, and optionally thesecond copolyester to an extruder using additive feeders, melt feedersor by preblending the pellets; 2) melting the polycarbonate, the firstcopolyester, and optionally the second copolyester in the extruder; 3)blending the polycarbonate, the first copolyester, and optionally thesecond copolyester by shearing action of the extruder screw to form amelt blend; and 4) cooling the melt blend to form clear pellets. Thetemperature settings of the extruder should be set at greater than 230°C., preferably greater than 250° C. The compounding process may useeither a single or twin screw extruders. Alternatively, the pellets ofthe polycarbonate, the first copolyester, and optionally the secondcopolyester may be placed directly into the extruder used to extrusionblow-mold the final articles, without a prior compounding step.

[0076] Known extrusion blow-molding techniques may be used to makeshaped articles or containers from the polymer blends of the presentinvention. A typical extrusion blow-molding manufacturing processinvolves: 1) melting the resin in an extruder; 2) extruding the moltenresin through a die to form a tube of molten polymer (i.e., a parison)having a uniform side wall thickness; 3) clamping a mold having thedesired finished shape around the parison; 4) blowing air into theparison, causing the extrudate to stretch and expand to fill the mold;5) cooling the molded article; and 6) ejecting the article from themold.

[0077] The polymer blends of the present invention are characterized bya novel combination of properties including low haze. Haze can bedetermined by two methods. The first method is visual observation of theblend extrudate where about 300 grams of the melt blended material iscollected in a pile and set aside and allowed to slowly cool to roomtemperature. The pile of cooled blend is then examined visually forhaze. The second method measures haze according to ASTM D1003 onextrusion molded bottle sidewalls using a HunterLab UltraScan Sphere8000. %Haze=100 *Diffuse Transmission/Total Transmission. Diffusetransmission is obtained by placing a light trap on the other side ofthe integrating sphere from where the sample port is, thus eliminatingthe straight-through light path. Only light scattered by greater than2.5 degrees is measured. Total transmission includes measurement oflight passing straight-through the sample and also off-axis lightscattered to the sensor by the sample. The sample is placed at the exitport of the sphere so that off-axis light from the full sphere interioris available for scattering. (Regular transmission is the name given tomeasurement of only the straight-through rays—the sample is placedimmediately in front of the sensor, which is approximately 20 cm awayfrom the sphere exit port—this keeps off-axis light from impinging onthe sample.)

[0078] The melt viscosity of the materials used herein is measured at240° C. and is determined with a Rheometrics Mechanical Spectrometer(RMS 800) with 25 mm parallel plates. Samples are vacuum dried at 70° C.overnight or longer before testing. The units are reported in Poise (P).

[0079] The glass transition temperatures (Tgs) of the blends weredetermined using a TA Instruments 2950 differential scanning calorimeter(DSC) at a scan rate of 20° C./minute. The values reported below arefrom the second DSC scan.

EXAMPLES

[0080] The polymer blends provided by the present invention and thepreparation thereof, including the preparation of representativepolyesters, are further illustrated by the following examples.

Comparative Examples 1-3 and Examples 1-5

[0081] Blends were prepared by combining polyester with polycarbonateand a phosphorus additive. A summary of materials used is shown in Table1.

[0082] The copolyesters and polycarbonates used in the blends are listedbelow and were prepared by methods well known in the art for thepreparation of high molecular weight polyesters.

[0083] Copolyester A is a branched copolyester comprising a diacidcomponent containing 100 mole percent terephthalic acid residues and adiol component containing 59-63 mole percent 1,4-cyclohexanedimethanol(CHDM) residues and 37-41 mole percent ethylene glycol residues and alsocontaining 0.18 mole percent trimellitic anhydride (TMA) residues.

[0084] Copolyester B is a branched copolyester comprising a diacidcomponent containing 100 mole percent terephthalic acid residues and adiol component containing 56 mole percent CHDM residues and 44 molepercent ethylene glycol residues and also containing 0.18 mole percentTMA residues.

[0085] Copolyester C is a branched copolyester comprising a diacidcomponent containing 100 mole percent terephthalic acid residues and adiol component containing 48-52 mole percent CHDM residues and 52-48mole percent ethylene glycol residues and also containing 0.18 molepercent TMA residues.

[0086] Copolyester D is a linear copolyester comprising a diacidcomponent containing 100 mole percent terephthalic acid residues and adiol component containing 62 mole percent CHDM residues and 38 molepercent ethylene glycol residues and also containing 0.18 mole percentTMA residues.

[0087] Copolyester E is a linear copolyester comprising a diacidcomponent containing 100 mole percent terephthalic acid residues and adiol component containing 81 mole percent CHDM residues and 19 molepercent ethylene glycol.

[0088] Polycarbonate X is a linear polycarbonate produced by DowChemical Company under the commercial name Calibre 300-10. It has a meltflow rate (MFR) of 10 measured according to ASTM D1238 at 300° C. usinga 1.2 kg mass.

[0089] Polycarbonate Y is a branched polycarbonate produced by DowChemical Company under the commercial name Calibre 603-3. It has a meltflow rate (MFR) of 3 measured according to ASTM D1238 at 300° C. using a1.2 kg mass.

[0090] The phosphorus concentrate (designated “conc” in Table 1) wasprepared by first compounding Weston 619, a distearyl pentaerythritoldiphosphite available from GE Specialty Plastics, into copolyester D ona single screw extruder at 270° C. This composition is thentumble-blended with 5 wt % water at 80° C. for 8 hours to hydrolyze theWeston 619. The final phosphorus content of the pellets is 5 weightpercent elemental phosphorus based on total pellet weight.

[0091] All blends were prepared on a Sterling 1.25 inch single screwextruder at 260° C. melt temperature and 90 rpm. The copolyesters weredried at 70° C., and the bisphenol A polycarbonate was dried at 120° C.overnight. In each blend example, 57 parts by weight of the copolyesterswere combined with 40 parts by weight bisphenol A polycarbonate and 3parts by weight of the phosphorus additive, except for ComparativeExample 2 where 47 parts by weight of the copolyester were combined with50 parts by weight bisphenol A polycarbonate and 3 parts by weight ofthe phosphorus additive.

[0092] Comparative Example 1 is an example of neat copolyester C. Thismaterial has a good shear thinning ratio, but does not possess asufficiently high glass transition temperature (Tg) for high heatapplications.

[0093] Comparative Example 2 is an example of a blend that does notcontain any branched copolyester. This blend does possess a sufficientlyhigh glass transition temperature for high heat applications, but doesnot have a high enough shear thinning ratio to be blown into bottles.

[0094] Comparative Example 3 is an example of a blend of polycarbonatewith a copolyester that has too low a level of CHDM. This blend is hazy.

[0095] Examples 1-5 are examples of the invention that possess highglass transition temperatures, possess good shear thinning ratios, andare free of haze. TABLE 1 Avg. Melt viscosity at 240° C. mole Shear CPECPE CPE CPE CPE % PC PC Tg Haze 1 400 thinning Ex. A B C D E CHDM X YConc (° C.) (visual) rad/sec rad/sec ratio CE-1 100 50 83 clear 470008400 5.60 CE-2 47 81 50 3 113 clear 17100 8700 1.97 CE-3 57 50 40 3 hazy31200 9000 3.47 E-1 57 56 40 3 clear E-2 57 62 40 3 clear 39300 100003.93 E-3 57 59 40 3 105 clear 46300 9800 5.55 E-4 32 25 64 40 3 106clear 36300 9700 3.75 E-5 32 25 56 40 3 104 clear 38300 9800 3.91

Comparative Example 4

[0096] Bottles were generated from the blends prepared in ComparativeExample 3 using an 80 mm Bekum H-121 continuous extrusion blow-moldingmachine fitted with a barrier screw. The materials were dried for 12hours at 65° C. (150° F.) prior to extrusion. The extruder was run at 12revolutions per minute (RPM) using a 215° C. (420° F.) barreltemperature and a 199° C. (390° F.) head temperature. The temperature ofthe melt was 232° C. (449° F.), measured by inserting a melt probedirectly into the parison 5mm out from the die. The materials wereextruded into water bottles having a volume of 3.785 liters (1 U.S.gallon), using a 100 mm die. The bottles weighed 175 grams. Haze in thebottle sidewall was measured to be 3.94%.

Example 6

[0097] Bottles were generated from the blend prepared in Example 1 usingan 80 mm Bekum H-121 continuous extrusion blow-molding machine fittedwith a barrier screw. The materials were dried for 12 hours at 65° C.(150° F.) prior to extrusion. The extruder was run at 27 revolutions perminute (RPM) using a 199° C. (390° F.) barrel temperature and a 199° C.(390° F.) head temperature. The temperature of the melt was 239° C.(452° F.), measured by inserting a melt probe directly into the parison5mm out from the die. The materials were extruded into water bottleshaving a volume of 3.785 liters (1 U.S. gallon), using a 100 mm die. Thebottles weighed 150 grams. Haze in the bottle sidewall was measured tobe 0.38%.

Example 7

[0098] Bottles were generated from the blend prepared in Example 2 usingan 80 mm Bekum H-121 continuous extrusion blow-molding machine fittedwith a barrier screw. The materials were dried for 8 hours at 65° C.(150° F.) prior to extrusion. The extruder was run at 21 revolutions perminute (RPM) using a 200° C. (392° F.) barrel temperature and a 190° C.(375° F.) head temperature. The temperature of the melt was 218° C.(425° F.), measured by inserting a melt probe directly into the parison5mm out from the die. The materials were extruded into water bottleshaving a volume of 3.785 liters (1 U.S. gallon), using a 100 mm die. Thebottles weighed 150 grams. Haze in the bottle sidewall was measured tobe 0.71%.

Example 8

[0099] Bottles were generated from the blend prepared in Example 3 usingan 80 mm Bekum H-121 continuous extrusion blow-molding machine fittedwith a barrier screw containing a Maddock mixing section. The materialswere dried for 8 hours at 65° C. (150° F.) prior to extrusion. Theextruder was run at 10 revolutions per minute (RPM) using a 232° C.(450° F.) barrel temperature and a 232° C. (450° F.) head temperature.The temperature of the melt was 249° C. (481° F.), measured by insertinga melt probe directly into the parison 5 mm out from the die. Thematerials were extruded into handleware bottles having a volume of 1.89liters (64 ounces), using a 70 mm die. The bottles weighed 120 grams.Haze in the bottle sidewall was measured to be 0.59%.

Example 9

[0100] Bottles were generated from the blend prepared in Example 4 usingan 80 mm Bekum H-121 continuous extrusion blow-molding machine fittedwith a barrier screw containing a Maddock mixing section. The materialswere dried for 8 hours at 65° C. (150° F.) prior to extrusion. Theextruder was run at 10 revolutions per minute (RPM) using a 232° C.(450° F.) barrel temperature and a 232° C. (450° F.) head temperature.The temperature of the melt was 250° C. (483° F.), measured by insertinga melt probe directly into the parison 5 mm out from the die. Thematerials were extruded into handleware juice bottles having a volume of1.89 liters (64 ounces), using a 70 mm die. The bottles weighed 90grams. Haze in the bottle sidewall was measured to be 0.67%.

[0101] The invention has been described in detail with particularreference to preferred embodiments and working examples, but it will beunderstood that variations and modifications can be made withoutdeparting from the spirit and scope of the invention, as defined by thefollowing claims.

We claim:
 1. A blend that is capable of being extrusion blow-molded,said blend comprising polycarbonate and copolyester.
 2. The blendaccording to claim 1, which comprises between 45 and 90 weight percentof the copolyester and between 10 and 55 weight percent of thepolycarbonate.
 3. The blend according to claim 1, which has a shearthinning ratio of at least about
 3. 4. The blend according to claim 1,wherein the polycarbonate has a melt flow rate between 2 and
 18. 5. Theblend according to claim 1, wherein the polycarbonate comprises abranching agent.
 6. The blend according to claim 1, wherein thecopolyester has an inherent viscosity of about 0.5 to 1.1 and a shearthinning ratio of at least about 5, and comprises: A. diacid residuescomprising terephthalic acid residues; B. diol residues comprising about52 to 75 mole percent of 1,4-cyclohexanedimethanol residues and about 25to 48 mole percent of ethylene glycol residues; and C. about 0.05 to 1.0mole percent of the residue of a trifunctional monomer.
 7. The blendaccording to claim 6, wherein the copolyester comprises A. diacidresidues comprising at least 40 mole percent of terephthalic acidresidues; B. diol residues comprising about 52 to 65 mole percent of1,4-cyclohexanedimethanol residues and about 35 to 48 mole percent ofethylene glycol residues; and C. about 0.05 to 1.0 mole percent of theresidue of a benzenetricarboxylic acid or anhydride.
 8. The blendaccording to claim 6, wherein the copolyester has an inherent viscosityof about 0.6 to 0.9, and comprises: A. diacid residues comprising atleast 40 mole percent of terephthalic acid residues; B. diol residuescomprising about 52 to 75 mole percent of 1,4-cyclohexanedimethanolresidues and about 25 to 48 mole percent of ethylene glycol residues;and C. about 0.1 to 0.25 mole percent of the residue of abenzenetricarboxylic acid or anhydride.
 9. The blend according to claim6, wherein the copolyester has an inherent viscosity of about 0.6 to0.9, and comprises: A. diacid residues consisting essentially ofterephthalic acid residues; B. diol residues consisting essentially ofabout 52 to 75 mole percent of 1,4-cyclohexanedimethanol residues andabout 25 to 48 mole percent of ethylene glycol residues; and C. about0.1 to 0.25 mole percent of trimellitic acid or anhydride residues. 10.The blend according to claim 6, wherein the trifunctional monomer isselected from the group consisting of tricarboxylic acids or estersthereof and aliphatic triols.
 11. The blend according to claim 10,wherein the trifunctional monomer is a benzenetricarboxylic acid oranhydride.
 12. A blend that is capable of being extrusion blow-molded,said blend comprising polycarbonate and at least one copolyester. 13.The blend according to claim 12, which comprises 45 to 90 weight percentof copolyester and 10 to 55 weight percent of polycarbonate.
 14. Theblend according to claim 12, which has a shear thinning ratio of atleast about
 3. 15. The blend according to claim 12, wherein thepolycarbonate has a melt flow rate between 2 and
 18. 16. The blendaccording to claim 12, wherein the polycarbonate comprises a branchingagent.
 17. The blend according to claim 12, which comprises about 40 to100 weight percent of a first copolyester and about 0 to 60 weightpercent of a second copolyester, wherein the first copolyester has aninherent viscosity of about 0.5 to 1.1 and a shear thinning ratio of atleast about 5, and comprises: A. diacid residues comprising terephthalicacid residues; B. diol residues comprising about 45 to 75 mole percentof 1,4-cyclohexanedimethanol residues and about 25 to 55 mole percent ofethylene glycol residues; and C. about 0.05 to 1.0 mole percent of theresidue of a trifunctional monomer, wherein the second copolyester hasan inherent viscosity of about 0.5 to 1.1 and a shear thinning ratio ofat least about 2, and comprises: A. diacid residues comprisingterephthalic acid residues; and B. diol residues comprising about 52 to90 mole percent 1,4-cyclohexanedimethanol residues and about 10 to 48mole percent ethylene glycol residues, and wherein the average amount of1,4-cyclohexanedimethanol residues in the first and second copolyestersis between 52 to 75 mole percent.
 18. The blend according to claim 17,wherein the first copolyester comprises: A. diacid residues comprisingat least 40 mole percent of terephthalic acid residues; B. diol residuescomprising about 45 to 65 mole percent of 1,4-cyclohexanedimethanolresidues and about 35 to 55 mole percent of ethylene glycol residues;and C. about 0.05 to 1.0 mole percent of the residue of abenzenetricarboxylic acid or anhydride.
 19. The blend according to claim17, wherein the first copolyester has an inherent viscosity of about 0.6to 0.9, and comprises: A. diacid residues comprising at least 40 molepercent of terephthalic acid residues; B. diol residues comprising about45 to 75 mole percent of 1,4-cyclohexanedimethanol residues and about 25to 55 mole percent of ethylene glycol residues; and C. about 0.1 to 0.25mole percent of the residue of a benzenetricarboxylic acid or anhydride,and wherein the second copolyester has an inherent viscosity of about0.6 to 0.9, and comprises: A. diacid residues comprising terephthalicacid residues; and B. diol residues comprising about 52 to 90 molepercent 1,4-cyclohexanedimethanol residues and about 10 to 48 molepercent ethylene glycol residues.
 20. The blend according to claim 17,wherein the first copolyester has an inherent viscosity of about 0.6 to0.9, and comprises: A. diacid residues consisting essentially ofterephthalic acid residues; B. diol residues consisting essentially ofabout 48 to 65 mole percent 1,4-cyclohexanedimethanol residues and about35 to 52 mole percent ethylene glycol residues; and C. about 0.1 to 0.25mole percent trimellitic acid or anhydride residues.
 21. A blend that iscapable of being extrusion blow-molded, said blend comprising: I. about1 to 99 weight percent of a polycarbonate comprising a diol componentcomprising about 90 to 100 mole percent of 4,4′-isopropylidenediphenolunits and about 0 to 10 mol percent modifying diol units having 2 to 16carbon atoms; and II. about 1 to 99 weight percent of a mixturecomprising: A. about 40 to 100 weight percent of a first copolyestercomprising: (1) diacid residues comprising terephthalic acid residues;(2) diol residues comprising about 45 to 75 mole percent of1,4-cyclohexanedimethanol residues and about 25 to 55 mole percent ofethylene glycol residues; and (3) about 0.05 to 1.0 mole percent of theresidue of a trifunctional monomer; and B. about 0 to 60 weight percentof a second copolyester comprising: (1) diacid residues comprisingterephthalic acid residues; and (2) diol residues comprising about 52 to90 mole percent 1,4-cyclohexanedimethanol residues and about 10 to 48mole percent ethylene glycol residues, wherein the average amount of1,4-cyclohexanedimethanol residues in the first and second copQlyestersis between 52 to 75 mole percent.
 22. The blend according to claim 21,which comprises between 45 and 90 weight percent of the mixture andbetween 10 and 55 weight percent of the polycarbonate.
 23. A method ofmaking a clear article from the blend of claim 21, said methodcomprising the steps of: (a) blending the polycarbonate, the firstcopolyester, and optionally the second copolyester; (b) before, during,or after step (a), melting the polycarbonate, the first copolyester, andoptionally the second copolyester to form a melt blend; and (c) coolingthe melt blend to form a clear article.
 24. A shaped article extrusionblow-molded from the blend of claim
 1. 25. A shaped article extrusionblow-molded from the blend of claim
 12. 26. A shaped article extrusionblow-molded from the blend of claim
 21. 27. A container extrusionblow-molded from the blend of
 9. 28. A container extrusion blow-moldedfrom the blend of
 20. 29. A container extrusion blow-molded from theblend of 21.